Computer-implemented systems have become complex and involve various entities such as data storage media, network components, data storage systems, memories, etc. Components of systems, such as data storage systems such as RAID (redundant array of independent disks) are themselves complex computer-implemented systems.
Networks and other systems may have various paths available which employ different ones of the entities.
An example of a data storage system comprises an IBM® ESS (Enterprise Storage Server) such as a DS8000, which has redundant clusters of computer entities, cache, non-volatile storage, etc.
The data storage system is accessed over networks, each of which comprises a plurality of entities, such as adapters, switches and communication links. The data storage may comprise a RAID system or other types of data storage. RAID systems may be arranged in various levels and with different numbers of data storage entities, thereby providing differences in reliability of the overall system.
Reliability of such computer-implemented systems is important and the systems are typically set up to provide optimum reliability and throughput, often with redundancy. Some types of activities require maximum reliability with less potential for failure as compared to other activities, for example, a write operation requires maximum reliability to insure that data is stored correctly, while a read operation may be repeated without harm to the data. The potential failure rates of the entities within the systems may be subject to change over time. These and other issues may affect the intended reliability.